The objective of project 3 is to identify on chromosome 5 a putative recessive oncogene--the "antileukemia gene (ALG)" whose homozygous inactivation in del(5q) leads to MDS or AML. Dr. Westbrook will complete a high-resolution physical map of the critical region, increasing the number of probes (including polymorphic sequences, cloned genes, and anonymous phage or cosmid clones). These materials will be used for direct analysis of patient cells as well as somatic cell hybrids, to map allele losses, translocations, and submicroscopic deletions, hoping to find structural abnormalities that will lead to the gene. When such regions are found, cloning in YACs, identification of expressed sequences, and functional studies of the gene(s) will be done. Known genes will also be investigated both genetically and functionally as ALG candidates, starting with EGR1 (in collaboration with Dr. Sukhatme). Dr. Westbrook will also work closely with Dr. Le Beau, who will concurrently be used these probes to determine the physical location of the ALG cytogenetically. A series of experiments is designed to better understand the structure of the hematopoietic genes that cluster on chromosome 5, to determine whether hemizygous loss of one or more of these genes plays a role in the development or progression of leukemia.